Integration of atmospheric intrusion sensors in electronic component packages

ABSTRACT

An apparatus for detecting an intrusion of an environmental substance into an environmentally sealed electronic components package. The electronic components package generally includes a plastic coated or plastic enclosed electronic component, that includes a printed circuit board and/or integrated circuits. The intrusion of the environmental substance into the electronic components package can be measured by one of a plurality of monitors. The monitors can detect the presence of the environmental substance and alert a user that a break in the seal of the electronic components package has occurred.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/219,693 filed on Aug. 15, 2002. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present teachings relate to a system to ascertain the integrity ofan electronic component, and particularly relates to a system toindicate moisture ingress or accumulation in a sealed system.

BACKGROUND

Electronic components form a large part of many modern machines anddevices. Furthermore, they are often integral to the proper operation ofsuch devices. Electronic components often include, integrated circuitsthat provide a very compact and efficient means for performing variouselectronic functions.

Although integrated circuit boards and chips provide an inexpensive wayto provide electronic components to many vehicles and structures, theyare not always impervious to the elements such as moisture and otherenvironmental contaminants that may harm electronic components. Inparticular, when these components are encased in plastic, differentenvironmental conditions may damage the circuits. The plastic of theintegrated circuits and chips are not completely impervious to moistureand environmental conditions. In addition, the plastic molded parts maybe damaged or harmed by other environmental conditions such as thermalshock or extent of cracking. If the electronic components, such asintegrated circuit boards, become damaged, then moisture may enter theenclosure surrounding circuit boards. If moisture is able to reach thecircuit board interface, then damage may occur, particularly, byshorting or corroding the internal components.

One commonly known solution has been to use hermetically sealedcomponents. Using hermetically sealed components, however, often greatlyincreases the cost of the component. These packages generally requirespecific and unique materials and manufacturing processes that haveassociated production costs. Although hermetically sealed components aregenerally known and accepted to have good seal longevity, it is desiredto produce a component which is cheaper and still able to have a highlongevity.

Moreover, it is easy to determine if a hermetically sealed component hasbeen compromised. That is, determining that a hermetically sealedcomponent has been damaged or the components inside the part where theseal may have been damaged could be determined by fine and gross leaktesting. The same is not true for integrated circuits or similarcomponents in plastic or other enclosures. Simply, there is no easy wayto determine whether the electronic component package has beencompromised, thus alerting a user to a possible or impendingmalfunction.

Therefore, it is desirable to produce a structure within the componentpackage that is able to determine if a seal, designed to protect theelectronic components from environmental conditions, has beencompromised. Moreover, it is desired to form such a component frominexpensive and generally available integrated circuit chips that may beintegrated into the circuit board, part, or enclosure (such as a box).Using generally availably components realizes cost reductions andinventory reduction which does not require specifically producing andformulating unique components for varying applications.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus for detecting moistureand associated environmental intrusions into an electronics package.Sensors determine whether moisture has entered an electronics package.In particular, sensors are used to determine the presence or absence ofan electric current which in turn determines whether moisture ispresent. The sensors are especially useful for items that have not beenhermetically sealed, but only generally sealed. For example, a silversensor is used to detect the gross or absolute intrusion of moistureinto an electronics package. The presence of moisture causes silver ionsto migrate and create an electrical short or conductive path in thesensor.

According to various embodiments a system for monitoring a sealedelectronics package for moisture or other elements that may have enteredthe sealed electronics package is taught. The system includes anelectronic component having a circuit. An envelope surrounds theelectronic component and a monitor determines the integrity of theenvelope. The monitor detects the presence of a substance in theenvelope.

According to various embodiments a system to provide substantialcertainty in the detection of a substance that has entered an internalenvironment intended to be sealed from an external environment istaught. The system includes a substantially sealed structure definingthe internal environment. A component and a monitor are disposed in theinternal environment. The monitor is able to determine the presence of asubstance from the external environment in the internal environment.

According to various embodiments a system to determine whether anelectronic components package is substantially free of an environmentalsubstance is taught. A structure defines an enclosed area substantiallyimpermeable to the substance. An electronic component is disposed in theenclosed area. The electronic component becomes damaged when contactedby a critical concentration of the substance. A sensor is disposed inthe enclosed area so that the monitor detects the presence of thesubstance before the substance reaches the critical concentration.

Further areas of applicability of the present teachings will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the various embodiments of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is an elevated view of an exemplary electronic components packageincluding a sensor, according to a first preferred embodiment of thepresent invention;

FIG. 2 is an enlarged and diagrammatic view of a substance monitoraccording to the first preferred embodiment of the present invention;

FIG. 3 is an enlarged and diagrammatic view of a substance monitoraccording to the first preferred embodiment of the present invention;

FIG. 4 is a perspective view of an electronics components packageaccording to a second preferred embodiment of the present invention; and

FIG. 5 is a perspective view of an electronics component packageaccording to a third preferred embodiment of the present invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The following description of various embodiments is merely exemplary innature and is in no way intended to limit the invention, itsapplication, or uses.

With reference to FIG. 1, a system 10 in accordance with a preferredembodiment of the present invention is shown for determining theintegrity of an electronic components package 11. The electronicspackage 11, typically includes a printed circuit board (PCB) 12 havingtraces 13 or integrated circuits (ICs) 14, and is provided with a firstseal failure monitor or sensor 16 a and a second seal failure monitor orsensor 16 b. Overlaying the PCB 12 is a sealing layer or portion 18 ofan appropriate plastic such as an epoxy substance. The sealing portion18 overlays or encases the entire PCB 12, or at least the portions thatmust be protected from environmental conditions or substances. Thesealing portion 18, the PCB 12, and any associated ICs 14 are an exampleof the electronic components package 11. Although it will be understoodthat the electronic components package 11 is not necessarilyhermetically sealed. That is the electronic components package 11 hasnot been positively or absolutely sealed from atmospheric intrusion.

It is desired to protect the PCB 12 and the accompanying components,such as the integrated circuits 14, and traces 13, from environmentalconditions and substances. One environmental substance is moisture thatmay short or corrode the integrated circuits 14 or the traces 13 on thePCB 12. Therefore, a leak in the electronics component package 11 may bemeasured by the monitors 16 a and 16 b and corrected before damageoccurs.

Although it may be inherently difficult to determine whether theelectronic components package 11 includes a defect, either due tomanufacture or wear, the appropriate monitors 16 a and 16 b may beincluded to determine if such a failure has occurred. Although manyappropriate moisture sensors may be used, comb or interdigitatedmonitors are particularly well suited to providing simple and accuratedetection of moisture in the electronic components package 11.

With reference to FIG. 2, the first monitor 16 a is illustrated. Themonitor 16 a, illustrated in highly simplified form as a gross moisturesensor, includes a probe 30 and a processor 32. The probe 30 includesconstituents such as silver. It will be understood that the probe 30 maybe formed of many different constituents not including silver, butsilver is particularly well suited for use in determining a grossmoisture leak. The probe 30 generally includes an anode comb 34 and acathode comb 36 that are in close proximity to each other. The anodecomb 34 includes anode teeth or digits 38. Similarly, the cathode comb34 includes cathode comb teeth or digits 40. The anode comb 34 and thecathode comb 36 are interdigitated, wherein each one of the anode digits38 is disposed between two parallel, adjacent cathode digits 40. Alsoincluded are an anode lead 42 and a cathode lead 44 that interconnectthe probe 30 and the processor 32. The processor 32 may then determinethe presence or absence of a current in the probe 30. Also, externalreadings may be taken as to current that is transferred or beingconducted between the anode comb 34 and the cathode comb 36.

The monitor 16 a may be formed in an appropriate size for theapplication. Spacing between the associated digits 38, 40 may also bevaried depending upon the requirements of the sensor 16 a. The morespace between associated digits the greater the time or amount ofmoisture to provide a signal. In one preferred implementation, thespacing between digits 38 and 40 is about 2 μm (0.08 mils) to about 25μm (1 mil). It will also be understood that the sensor 16 a illustratedin FIG. 2 is not illustrated to scale. The sensor 16 a, when it is madeof a silver compound on an IC, is generally square and preferablybetween about 40 and about 80 mils on a side.

Also, the sensor 16 a may be integrated into the PCB 12. The combs 34and 36 may be laid on the PCB 12 and the appropriate leads 42 and 44affixed to the combs 34 and 36. Therefore, the sensor 16 may be providedon the PCB 12 without greatly increasing the size or weight of the PCB12. This is particularly a concern in weight sensitive applications suchas aircraft and space vehicles.

Alternatively, the monitor 16 a may be first formed as a separatecomponent IC and then added to the PCB 12. For example, the combs 34 and36 may first be formed on a separate PCB and then added to the PCB 12 toprovide a moisture sensor to the PCB 12. Nevertheless, the addition ofthis extra part does not tangibly increase the size or weight of theelectronic components package 11. Moreover, the compact dimensions ofthe sensor 16 a allows a plurality of sensors 16 a to be added to anappropriate sized PCB 12 depending upon the size and distance betweenthe moisture sensitive components.

The sensors 16 a and 16 b may be made more sensitive to moisture thanother environmental conditions. Although it will be understood thatother appropriate sensors may be used to detect other environmentalleakages into the electronic components package 11. The sensor 16 a,including a silver sensor, determines a gross amount or the absolutepresence of any leak of moisture into the electronic components package11. That is, any moisture leak, regardless of the degree, may bedetected using the sensor 16 a leading to a short. When the anode comb34 and cathode comb 36 include silver ions, the silver ions becomemobile when water is present between the digits 38 and 40 of the combs34 and 36. Essentially, the silver sensor has substantially no currentwhen there is no moisture present. Upon the presence of moisture on thesilver sensor 16 a, silver ions are able to transfer from one digit 38,40 to another, thereby providing a current between the two combs 34, 36of the silver sensor 16 a. Therefore, the presence of generally anyamount of moisture, which is able to interconnect two digits of thecombs 34 and 36 the sensor 16 a, causes a signal to be produced by themonitor 16 a. The processor 32 provides a potential to the monitor 16 aand detects a current flow from the anode comb 34 to the cathode comb36, that only occurs when moisture is present. A user may then repair orreplace the electronic components package 11 or any portion thereof.

Second exemplary sensor 16 b, illustrated in detail in FIG. 3, comprisesa nichrome sensor. The nichrome sensor 16 b includes a combination ofnickel and chromium layers layered one atop the other. The nichromesensor 16 b is also relatively small and generally forms a rectanglehaving side lengths of preferably about 50 mills by about 100 mills.Again, it will be understood that the size of the nichrome sensor 16 bmay be altered depending upon the size necessary for the particularapplication.

The nichrome sensor 16 b also includes an anode comb or labyrinth 46 anda cathode comb or labyrinth 47. The anode comb 46 includes anode digits48 which are associated with cathode digits 49 of the cathode comb 47.The anode comb 46 may also include an anode lead 42′ and the cathodecomb a cathode lead 44′ that interconnect the combs 46 and 47 to aprocessor 32′. Therefore, the combs 46 and 47 define a probe 30′ thatprovides a signal, or which is used by the processor 30′ to create asignal, based on the sensing of the probe 32′.

The nichrome sensor 16 b comprises a more precise or quantitativemoisture detector. In particular, the nichrome sensor 16 b may determinequantitatively the amount of moisture which has leaked into theelectronic components package 11. Therefore, at least two levels ofmoisture detection may be provided for the electronic components package11. The silver sensor 16 a provides a “gross” leak indication orabsolute detection of whether moisture is present or not. The nichromesensor 16 b, on the other hand, can determine quantitatively the amountof moisture which has entered the electronic components package 11.

The nichrome sensor 16 b provides a resistance output value when nomoisture is present. The presence of moisture decreases the amount ofresistance between the digits of the nichrome sensor 16 b. Therefore, asthe concentration of moisture increases, the resistance measured usingthe nichrome sensor 16 b decreases. Therefore, a plot or determinationof the amount of resistance in the nichrome sensor 16 b depends upon theconcentration of moisture, thus allowing a quantitative measurement ofmoisture.

In addition, other appropriate sensors may be used to determine moistureleaks. For example, an integrated microchip sensitive to corrosion canbe used. One such chip is the ATC04 chip produced by Sandia®. The ATC04is an integrated chip that includes ring oscillators as moisture andcorrosion sensors and other sensors such as stress and temperaturesensors. Nevertheless, the inclusion of such a chip in the electroniccomponents package 11 can be used to determine whether the seal of theelectronic components package 11 has become compromised.

With reference to FIG. 4, an electronic components package 50 accordingto a second preferred embodiment of the present invention isillustrated. The electronic components package 50 includes a firstmoisture sensor 52 and a second moisture sensor 54 spaced a distanceapart. The electronic package 50 includes a three dimensional boxstructure 55 that forms an enclosure or encasement of a sealedcompartment that includes several PCBs 60 and other integrated circuitchips 62. The electronic components package 50, nevertheless, must besealed from the outside ambient environment. Therefore, the presence ofthe moisture sensors 52 and 54 provide a means of measuring the amountof any moisture that enters the electronic components package 50.

Therefore, it will be understood that the moisture sensors 16 a, 16 b,52 or 54 of the present invention may be used singly or as a pluralityto determine the moisture present in an electronic components package ormodule. As an example, if the electronic components package is larger itmay be desirable to include a plurality of moisture sensors in severaldifferent areas to determine whether moisture has entered any of thoseareas or might be affecting any of the circuitry in separate andselected areas. Conversely, if the electronic components package ormodule is substantially smaller, only one or two moisture sensors may bedesired. In addition, different types of moisture sensors may beprovided to measure both a gross moisture leakage and to quantify theamount of moisture which is present in the electronic component package.

With reference to FIG. 5 an electronic components package 70 accordingto a third preferred embodiment of the present invention is illustrated.The electronic components package 70 generally includes an integratedcircuit which may be soldered onto a PCB, such as the PCB 12. Theelectronic components package 70 includes a plurality of leads 72 whichallow the interconnection between the PCB and the electronic componentspackage 70. Any number of circuits or resistors may be included withinthe electronics component package 70. These components are thenencapsulated or encased in a solid plastic case 74. Also encapsulatedwithin the case 74 is a sensor 76. Although any number of the sensors 76may be included, the electronic components package 70 is typicallyrelatively small in size, and thus may only require one sensor 76.Nevertheless, it will be understood that the sensor 76 is highlyfunctional and may be placed in a very small electronic componentspackage 70.

With the present invention, electronic component packages or modulesthat have not been hermetically sealed may be used in sensitiveapplications. The use of moisture sensors allows an easy and quick meansto determine whether the electronic component package seal has beencompromised. From this determination, it is then known that moisture maybe present that will likely disrupt the operation of the electronics inthe electronic components package.

The teachings herein are merely exemplary in nature and, thus,variations that do not depart from the template of the teachings areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theteachings.

1. A system for detecting if a sealed environment containing a componenthas been compromised, said system comprising: a substantially sealedstructure defining said sealed environment; a component disposed in thesealed environment; a monitor disposed in the sealed environment; andwherein said monitor is able to determine the presence of an externalsubstance in the sealed environment, thereby indicating that the sealedenvironment has been compromised.
 2. The system of claim 1, wherein saidmonitor includes: a probe; wherein said probe includes a silverconstituent; and a processor to determine the presence of the substanceaffecting said probe.
 3. The system of claim 1, wherein said monitor isable to quantify an amount of the substance in the sealed environment.4. The system of claim 3, wherein said monitor includes: a probeincluding at least one of the group consisting of a nickel constituentand a chrome constituent; a processor to determine the presence of thesubstance affecting said probe; and wherein said processor is able toproduce a signal dependant upon the presence of the substance affectingsaid probe.
 5. The system of claim 1, wherein said component includes aprinted circuit board; and wherein said substantially sealed structureincludes a sealing polymer overlaying said printed circuit board to forma substantially sealed area between said printed circuit board and saidsealing polymer.
 6. The system of claim 1, wherein the substancedetected by said monitor includes water.
 7. The system of claim 1,including a plurality of said monitors; and wherein one of saidplurality of monitors is placed in said structure to determine thepresence of a compromise of the sealed environment of said structure ina selected portion of said structure.
 8. The system of claim 4, whereinsaid probe changes resistance when exposed to a selected concentrationof an aqueous substance.
 9. A system to determine whether an electroniccomponents package is substantially free of an environmental substance,comprising; a polymer structure defining an enclosed area impermeable tothe substance; an electronic component disposed in said enclosed area,wherein said component becomes damaged when contacted by a criticalconcentration of the substance; and a monitor disposed in said enclosedarea, wherein said monitor is adapted to detect the presence of thesubstance before the substance reaches the critical concentration. 10.The system of claim 9, wherein said sensor includes: a probe, whereinsaid probe includes a silver constituent; and a processor to determinethe presence of the substance affecting said probe.
 11. The system ofclaim 9, wherein said monitor is able to quantify an amount of thesubstance in the enclosed area.
 12. The system of claim 9, wherein saidsensor includes: a probe consisting of at least one of the group: anickel constituent and a chrome constituent; a processor to determinethe presence of the substance affecting said probe; and wherein saidprocessor is able to produce a signal dependant upon the presence of thesubstance affecting said probe.
 13. The system of claim 9, wherein thesubstance detected by said monitor includes water.
 14. The system ofclaim 9, including: a plurality of said monitors; wherein one of saidplurality of monitors is placed in said structure to determine thepresence of the substance in a selected portion of said structure; andwherein said one of said monitors produces a signal when a selectedconcentration of the substance exists in the selected portion.
 15. Thesystem of claim 9, wherein said monitor is adapted to change resistancewhen the critical concentration is reached.
 16. A method of determiningwhether a seal has been breached, comprising: providing an electroniccomponent; encasing the electronic component to substantially seal theelectronic component from a substance in an ambient environment; andproviding a monitor in the encasement to determine whether the externalsubstance has penetrated the encasement.
 17. The method of claim 17,further comprising: providing a single from the monitor if the externalsubstance enters the encasement to a critical concentration.
 18. Themethod of claim 17, wherein the signal includes a change in a currentpassing through the monitor.